The present invention relates to a film carrier type substrate used, for example, for high density mounting of integrated circuits, which is based on the film carrier system, and to a method of manufacturing the film carrier type substrate.
The film carrier system among (IC) integrated circuits mounting techniques has attracted a special attention because of its advantageous features of a continuous IC mounting process and high bonding speed.
The film carrier type substrate used for the film carrier system is conventionally categorized into two types of substrates. (1) The first type of substrate is shown in FIG. 1. As shown, a copper foil 13 is bonded onto a film 11 by means of adhesion 12. The copper foil 13 thus bonded is etched to form a pattern of a desired electric circuit. (2) In the second type of substrate, an electric pattern made of copper, nickel or the like is formed on the surface of the film 11 by non-electrolytic plating process. In either type of substrate, the film 11 is made of an organic high molecular substance, mainly polyimide.
The substrate with a copper foil bonded thereto, involves the following disadvantages. (1) Since the adhesion layer 12 is interlayered between the film 11 and copper foil 13, poor thermal conductivity is present between them. (2) The adhesiveness between the film 11 of polyimide or the like and the copper foil 13 is unsatisfactory. (3) When the film carrier type substrate undergoes temperature of 150.degree. or more for a long time, the bonding of the film 11 and the copper foil 13 is remarkably deteriorated.
The substrate formed by the non-electrolytic plating process as wet process is disadvantageous in that (1) adhesion properties of the plating layer is not uniform, and (2) a strict management is required for plating solution to avoid environmental pollution.